Liquid oxygen converter



"12: will 5? July 5, 1960 H. B. LEWIS 2,943,454

LIQUID OXYGEN CONVERTER Filed June 30, 1958 2! press 0, 22 1e 54 1e 15 52 2 17 W Pass Chem Del; very I 5 19 E om/ar 60 I Venf w"- 1/ g 25 I I6: 1'

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Valve 12012! dark- Bur B 5a A of/lmen'ca. Milo/ml 71 45! filling! Jsson'a tiorz, Execafor BY MS lrmmugs iii/221 14/50, JWsrE/e uq eezs.

LIQUID OXYGEN CONVERTER Howard B. Lewis, deceased, late of Newport Beach, Calif.,

by Bank of America National Trust 8; Savings Association, executor, Santa Ana, CalifL, assignor to Mine Safety Appliances Company, Pittsburgh, Pa, a corporation of Pennsylvania Filed June 30, 1958, Ser. No. 745,650

9 Claims. (Cl. 62--S1) This invention relates to a device for storing a normally gaseous liquid, such as liquid oxygen, converting the same to a gas as desired, and delivering the gas to a point of use at a predetermined rate or in a range of predetermined rates.

Conventional types of such devices are commonly known as liquid oxygen converters, and are employed in aircraft to supply gaseous oxygen to the crew members and passengers as required. Such conventional devices include an insulated flask, normally of the double-walled vacuum type for retaining an adequate supply of liquid oxygen for a suitable period of time at a desired pressure and temperature. They also include a suitable evaporator adapted to receive liquid oxygen from the flask and evaporate it to gaseous form for delivery to a supply line to a point of use.

Such conventional liquid oxygen converters have had many disadvantages and deficiencies and have not been fully satisfactory. For example, they have been unable to deliver a uniform supply of gaseous oxygen under varying demand conditions over adequate periods oftime. The liquid or gaseous oxygen under varying demand: conditions sometimes surges from the delivery line back into the flask, thereby warming the contents of the flask and increasing the pressure therein, with an. attendant, undesirable loss of part of the contents through the pressure relief valve normally employed in such a system. Again, liquid or gaseous oxygen frequently becomes trapped in the system exterior to the flask and tends to surge in the lines, thereby materially changing the rate of delivery of gaseous oxygen from the device, which is also very undesirable. Changes in the internal pressure in the flask may substantially alter the delivery rate and the rate of loss of the contents.

It is a primary object of this invention to provide such a liquid oxygen converter device which will retain a supply of oxygen in the flask thereof at a substantially uniform pressure regardless of changes in ambient temperature and regardless of varying demand requirements on the system.

Another object of the invention is to provide such a device which will provide a substantially constant rate of delivery of gaseous oxygen to the user, but variable by the user to vary the delivery rate as desired over a wide range, and in which surging or pulsating of the flow of gaseous oxygen is reduced to a minimum.

A further object of the invention is to furnish such a device in which liquid oxygen which has passed from the. flask, and part of which has perhaps gasified in the connecting lines, will not return to the flask to increase the temperature of its contents with an attendant increase in pressure.

Still another object of my invention is to provide such a device having a system for quickly building up and maintaining the desired pressure in the flask.

A further object of the invention is to provide such a device in which there will be no surging of fluid in the lines of the system.

f ates Patent 2,943,454 Patented July 5, 1960 Another object is to provide a device of this character in which the fluid pressure in the flask is maintained substantially constant without substantial loss of the contents of the flask or the system through associated pressure relief valves.

It is a particular object of the invention to provide with such a device a pressure build-up system external to the flask but connected thereto which will operate to accomplish some of the foregoing objects and which is substantially separate from the delivery system for delivering the contents from the flask.

Another object is to providewith such a device an evaporator adapted to quickly and completely vaporize liquid oxygen so as to eliminate trapping of the liquid therein or in the delivery line leading therefrom.

Other objects and advantages will appear from the following specification and the drawings, which are for the purpose of illustration only, and in which:

Fig; 1 is a schematic flow diagram illustrating the invention; and

Fig. 2 is an enlarged vertical section taken through the lower end of the device shown in Fig. 1.

Referring to Fig. 1 of the drawing, the apparatus of this invention includes an insulated flask 10, a build-up pipe 11, having a build-up check valve 1'2 in the line thereof, a pressure closing valve 13, a vent valve 14, a delivery pipe 15, a liquid evaporator 16, a delivery check valve 17, a pressure relief pipe 18, a pressure relief valve 19, a thrift pipe 20, a pressure opening valve 21, and a by-pass check valve 22.

The insulated flask it), as best illustrated in Fig. 2, isof the conventional double walled vacuum type, in cluding an inner wall 24 and an outer wall 25 separated by a space 26, normally evacuated, the flask having a cylindrical closed compartment 2'7 at its lower end. As shown in Fig. 1, the flask has a main body portion 28 which is generally spherical in form and an upstanding neck 29 closed by a suitable cap 30.

As best shown in Fig. -2, the lower end of the inner wall 24 of the flask 10 is provided with a circular opening 32 into which is fitted a valve body 33 of the buildup check valve 12, the valve body being secured in gastight relation to the inner Wall by welding or otherwise. The valve body 33 includes an inlet port 34 communicating with the interior of the flask 10 and with a valve port 35 in turn communicating with an outlet port 36, the valve port being provided with an annular valve seat 37 upon which is adapted to seat a poppet type check valve 38, the same being guided for vertical movement in a spider 39 threaded into the bottom of a plug 40.

Connected into the outlet port 36 is one end of a lower portion 42 of the build-up pipe 11, the other end of which communicates through a fitting 43 through the wall of the compartment 27 with the main portion 44 of the build-up pipe.

Suitably connected to the bottom of the compartment 27 is the liquid evaporator 16 which preferably includes thin annular conical inner and outer walls 46 and 47 separated by an annular conical space 48 which terminates at its apex in an inlet opening 49 and at its lower end in an annular groove 59 which communicates with an outlet fitting 5 1 to which is suitably connected an outer end portion 52 of the delivery pipe 15. The inlet opening 49 communicates with an inlet fitting 53 to which is connected the body portion 54 of the delivery pipe 15. As shown in Fig. 1, the main portion 44 of the build-up pipe 11 connects between the fitting 43 and the pressure closing valve 13. The pressure closing valve 13 may be of any conventional type. It is connected in such a manner as to open when the pressure in the build-up line 11 falls below a predetermined value, and close when such pressure rises above such value.

In the line of the build-up pipe 11, disposed between the pressure closing valve and the top of the flask 10, are the vent valve 14 and the relief valve 19. Vent valve 14 may be of any conventional type of three-way valve adapted to be manually operated to either open communication through the build-up pipe above and below the valve, to close such communication entirely, or to open communication through the build-up pipe and a vent line 56 and to close ofi communication with the main portion 44 of the build-up pipe. The pressure relief valve 19 also may be of any conventional type adapted to permit a flow of gas from the build-up pipe 121 to atmosphere in response to a predetermined rise in pressure in the buildup pipe, but preventing a reverse flow. Such relief valve may be of the spring biased type, and is normally set to open when the pressure in the pressure relief build-up pipe 11 or in the thrift pipe 20 rises above a predetermined value which is substantially above the normal operating pressure of the system, such as, for example, approximately 30 p.s.i. above the system pressure. The upper end of the build-up pipe 11 communicates through a stub tubing 57 with the interior of the neck 29 above the normal level of liquid oxygen 58 contained in the flask 10.

Connected into the buildup pipe 11 between the vent valve 14 and the stub tubing 57 is one end of the thrift pipe 20. In the line of the thrift pipe 20 are the relief valve 19, and the pressure opening valve 21. Valve 21 is of any conventional type adapted to open when the pressure in the thrift line 20 rises above a predetermined pressure and to close when the pressure in the thrift line falls below such predetermined pressure. The pressure closing valve 13 and the pressure opening valve 21 may be of the conventional bellows-operated type in which a bellows connected to a valve poppet is subjected to'the pressure in the respective lines in which the valves are connected, so that an increase or decrease of pressure in the line will cause the valves to open or close as desired.

The other end of the thrift pipe 20 is connected to the pressure relief pipe 18 which, in turn, is connected to the liquid delivery check valve 17. Connected to the delivery check valve 17, and extending downwardly therefrom, is a discharge tube 59 which extends downwardly into the flask It) to a point adjacent its bottom and below any normal level of liquid oxygen therein. The delivery check valve 17 may be of any conventional poppet type, or may be similar to the build-up check valve 12, being adapted to permit a flow of fluid from the flask upwardly through the discharge tube 59 and into the delivery check valve, but preventing a reverse flow thereof.

The body portion 54 of the delivery pipe is connected into the pressure relief pipe 18 at a point between the delivery check valve 17 and the pressure open ing valve 21. The outer end portion 52 of the delivery pipe 15 communicates with a point of delivery or use through a manual shut-off valve 60.

The by-pass check valve 22 communicates between the build-up pipe 11 at a point between the relief valve 19 and the top of the flask 10 and with the thrift pipe 20 at a point between the pressure opening valve 21 and the delivery check valve 17. By-pass check valve 22 may be .a conventional type check valve adapted to permit a flow of gas from the body portion 54- of the delivery pipe 15 to the top of the flask via the stub tubing 57 end of the build-up pipe 11, but to prevent a reverse flow of the gas.

In operation, the flask 10 is partially filled with liquid oxygen to a level below the stub tubing 57, and the vent valve 14 is set to open communication through the build-up pipe 11 between the bottom and top of the flask. The build-up pipe 11 is the only connection openlnginto the bottom of the flask 10. It can be made of relatively small diameter tubing to keep the build-up volume small and thus speed up the build-up process which preferably should require a time elapse of only several seconds rather than minutes. In the present system this is accomplished by efficiently applying a relatively small amount of available heat to rapidly vaporize a small amount of liquid oxygen and thus quickly produce the desired oxygen pressure without heating the entire mass of liquid in the flask 10. The build-up oxygen pressure thus produced by vaporizing a small amount of liquid is introduced, through build-up line 11 and the top of flask 10, into the gas space in the flask. Some condensation of the thus introduced gaseous oxygen will take place on the cold surface of the liquid in the flask, but this action is relatively slow, so that it is possible to quickly produce an oxygen gas pressure over the liquid in the flask substantially above the vapor pressure of the liquid oxygen in the same flask. Stratification of warmer liquid oxygen at the surface of the liquid mass in the flask also assists the accomplishment of this state of affairs. The process of rapid build-up then reduces itself to drawing a small amount of liquid oxygen from the bottom of the flask at a controlled rate, rapidly evaporating it, and reintroducing the produced gaseous oxygen into the gas space in the top of the flask.

During the build-up of pressure in the system liquid oxygen may freely flow from the bottom of the flask 10 through the build-up check valve 12 and into the buildup pipe 11, and normally does so by reason of the hydrostatic head of liquid oxygen above the build-up check valve. Also conducive to such flow is the downwardly sloping pig tail formed by the lower portion 42 of the build-up pipe 11, and this is a feature of the invention. Since the ambient temperature about the build-up pipe 11 tends to warm up any liquid or gaseous oxygen contained therein to increase pressure in the build-up pipe, in the absence of the buildup check valve 12 such warmed liquid or gaseous oxygen in the build-up pipe would tend to re-enter the lower end of the flask, which would in turn raise the temperature of the liquid oxygen therein, which is very undesirable. The build-up check valve prevents such reverse flow, and such valve and its location immediately adjacent to the bottom of the flask 10 are important features of the invention. The buildup check valve 12 not only prevents warm oxygen from re-entering the bottom of the flask, with the undesired result noted, but, additionally, prevents any pressure surges developing in the build-up pipe 11 from being communicated to the bottom of the flask and the liquid therein, a common fault with conventional liquid oxygen converters. Furthermore, the build-up check valve 12 assures that all liquid oxygen leaving the flask there through and passing into the build-up pipe 11 is evaporated therein. Also, the build-up check valve 12, by preventing back flow of fluid from the build-up pipe into the flask, minimizes fluid surging in the system, and the time required for building up the system pressure to normal is reduced.

As an additional safeguard, to provide for any liquid oxygen that may be trapped in the build-up pipe 11 between the pressure-closing valve 13 and the build-up check valve 12, a relief valve function may be incorporated in the check valve 12 to permit a slow feed-back or release-back into flask 10 of any excess of pressure that may develop in the build-up pipe 11 under some circumstances. This may be accomplished by the use of an imperfect liquid check valve 12 such as may be produced by forming a scratch in the seat of the valve. Alternatively, a spring-loaded relief valve (not shown) sensitive to the difference in pressure across the pressure closing valve 13 could be used and could be set at any differential above the hydrostatic pressure head available to cause flow through the build-up line (which is usually less than about one pound per square inch) up to a safe maximum pressure.

When the normal operating pressure, say 70 p.s.i., has been attained, such pressure will exist in the flask 10 .aboye the liquid level therein, in the build-up pipe-11, in the thrift pipe20 in the pressure relief pipe 18, and in the clelivery pipe 15. v s I,

,When the delivery shut-off valve "lifl is opened, gaseous oxygempreferably at breathable temperaturejilows from the d v ry r pe t he P int f m?- h s dHQ the pressure in pressure relief pipe the thrift pipe 20 between the pressure opening 21 and the pressure relief pipe. Normal operating pressure in the build-up pipe, 11 and inthespaeeabove the liquid level in the flask 10 forces liquid oxygen upwardly through the discharge tube 59, through. the delivery check valve 17, into the delivery pipe 4 frornwhichit flows into the evaporator 16, Such liquid oxygen enters the evapor 16 h ug hei l t open g dfiqws ard y r yt 9s h hes a al S Dnr n t pa a t qu h he evapo o 161t i ui oxygen is warmed to cause its change to gaseous state ll ll v is V l h delivery P and delivery valve 60 to the point of use The evaporator 6 c ve t al iqui x e fl i e s n t reas ous state, which is animportant feature pf the invention.

Maintenance, of uniform delivery pressure appears to depend primarily upon two faOlQIS-Y First, the pressure in the flask 10 should be maintained as nearly uniform as possible. This is accomplished in the present converter by the use of a build-up system asindependentas possible of pressure fluctuations inthe delivery system.

Second, all liqui d entering thedelivery system should beevap ats rp nt y o p e t pp n q i w h upon evaporation afterdemand of gas has decreased, causes an undesirable ever-all pressure increase 'rhis e o d. f ct ris takensare by e nt an e pdoxygen and thefambi ent atmosphereand has relatively small liquid-containing space and short liquid passages. The, conical evaporator 16, possessing evaporating {characteristics quite superior tofa ,eoiledtubing evaporator,

spreads the liquid oxygen entering inlet opening 49 over I.

the relatively largefsurface, o'fJ-the conical space '48 in intimate contact with a substantial mass of metal exposing considerable surface ar eas to the atmosphere to .mined value the pressure closing valve'll; opens to permit a flow of liquid oxygen through the build-up pipe,where it is evaporated by ambient heatand buildsup the pressure to the desired operatingpressure in'the'sys'tem. So long as oxygen is delivered from the delivery pipe 15 this build-up of 'pressureinthe build-up' pipe "11 andin the air space in the flask continues to compensate for the loss of pressure due to such delivery of oxygen to the point of use. Suchbuild-up is substantially instantaneous to prevent a significant drop in system pressure due to delivery flowfrom thesyst'ein.

When the delivery shut-oil? :valveGO is "closed, the delivervof liquid oxygen from theflask 10 throughthe discharge tube 59 stops, the 'prssure closing'v'alv e l3 closes, the delivery check valve 17 closes, and any excess pressure in the delivery pipe 15 is communicated to the top of the flask 10 through the thrift pipe 20 and the upper end of the build-up pipe 11. A substantially constant pressure is maintained in this manner.

Any liquid oxygen trapped in the delivery hne 15 or evaporator 16 cannot flow back into the flask through the discharge tube 59, due to the operation of the delivery check valve 17, but instead passes back into the top of the flask through the thrift pipe 20.

Thusjthe conical surfacestructure of .rat0r...16 .w ehfpre entslarge C n ac ar a ztq o h l i 1 v 'riorr'r'ial de er-arias 'vvhem'thehelivei'y valve 60 is intenaitteauydpsaea and closed, pressure surgestend todvelp in the system upstream from the delivery valv 'e. :Siich fsurges cannot "force liquid or gas down- :wardly through the discharge tubing 59 into theflask, by re'ason of the delivery check valve 17. Similarly, urge cannot be communicated to the liquid in the bottom ofthe flask, by reason of the build-up check valve 12 if the build-up line is open, but, instead are communicated through the thrift pipe 20 andb'y-p'a'ss check valve 22 to the gas space in the flask which acts as a damping means to absorb such surges, and this is another important feature of the invention. U Thusthis, arrangement employing by-pass check valve 22 permits both -excess liquid or gaseous oxygen 'situations to be corrected smoothly and efiiciently by causing the excess oxygen to flow back into the gas space in the flask 10 'rather'than into the liquidin the flask. This makes 'use of the gas space as a surge damping receiver with a ,ininimum'of heattr'ansmission to the liquid oxygen, Transmission of heat to the liquid oxygen in flask 1 0, as pointed out above, is very'undesirable because it causes an increasein the pressure inside the flask, uneven operation and loss of oxygen through the pressure relief valve 19. Instead of using a separate by-pass check valve 22, as shown in Fig. 1 of the drawing, a modified pressure opening valve 21 may be used which incorporates the by-pass feature of valve 22 together with the pressure "opening feature in a single valve 21. In the flask 10 the portion containing liquid oxygen is ,referred "to herein as its liquid phase section and the portion above the level of suchliquid is referred to herein as its gas phase section. The build-up pipe 11 communicating between such liquid and gas phase sections. is referredto hereinas the build-up 'circult. The delivery pipe 15, -evaporator 16, the delivery check valve 17, and the discharge tube 59 'are referred to herein as'the supply circuit. The thrift pipe 20- and pressure opening, valve 21are referred to herein as the thrift circuit, of which the by-pass check valve 22 may be aIpart, Although a preferred embodiment of the invention has een shown,'it;is not'intended to limit the patent thereto but it'is' desired that itb'e' aifordedthe 'full scope of the following claims.

,What is'claimed is: s, s 1. In a;c'oiiverter of the character described, the com- 'bin'ation of:;ai1 insulated fiaskadapted'to receive liquid gasto aflevel below the top of the flask; a build-up pipe communicating between the'bottom of the flask and the top' Eif'th'e flask above said level; ab'uild-up check valve in the line of said build-up pipe and adjacent to the bottom of the flask, adapted to permit a free flow of liquid from the flask into the build-up pipe but preventing a reverse flow; 'a pressure 'closingvalve in said build-up pipe'betweensaidbuildhlp check valve "and the top of .the fiask, adapted to close when'the pressure in"'said build-up pipe'r'ises to a'predeterniined value and to open when it falls below the determined value; a delivery-pipe -ct'im'rnu'nieating"between the interior of said flask below 'fsaidliquid level and a delivery-point exterior of said flask; a :liqu'id'f evaporator in said delivery pipe between lthe'j'flask and said delivery point adapted to convert liquid 'flo'vviiig "fro said "flask through said delivery pipe to a as to be delivered to said delivery point; a delivery check valve in said delivery line between said flask and said evaporator adapted to permit a free flow of liquid through said delivery pipe from said flask to said evaporator but preventing a reverse flow thereof; a pressure relief pipe connected to said delivery pipe at a point between said delivery check valve and said evaporator; and a pressure relief valve in said pressure relief pipe adapted to relieve the pressure in said delivery pipe when it rises above a predetermined value.

2. In a converter of the character described, the combination of: an insulated flask adapted to receive liquid to a level below the top of the flask; a build-up pipe communicating between the bottom of the flask and the top of the flask above said level; a build-up check valve in the line of said build-up pipe and adjacent to the bottom; of the flask, adapted to permit a free flow of liquid from the flask into the build-up pipe but preventing a reverse flow; a pressure closing valve in said build-up pipe between said build-up check valve and the top of the flask adapted to close when the pressure in said build-up pipe rises to a predetermined value and to open when it falls below the predetermined value; a delivery pipe communicating between the interior of said flask below said liquid level and a delivery point exterior of said flask; a liquid evaporator in said delivery pipe between the flask and said delivery point adapted to convert liquid flowing from said flask through said delivery pipe to a gas to be delivered to said delivery point; a delivery check valve in said delivery line between said flaskand said evaporator adapted to permit va free flow of liquid through said delivery pipe from said flask to said evaporator but preventing a reverse flow thereof; a pressure relief p'ipe connected to said delivery pipe at a point between said delivery check valve and said evaporator; a pressure relief valve in said pressure relief pipe adapted to relieve the pressure in said deliv'er'y pipe when it rises above a predetermined value; a thrift pipe communicating between said build-up pipe at a point between said pressure closing valve and said flask and said pressure relief pipe at a point between said delivery check valve and said pressure relief valve; and a pressure opening valve in said thrift pipe adapted to open when the pressure in said thrift pipe exceeds a predetermined value and to close when said pressure falls below the predetermined value.

3. In a converter of the character described, the combination of: an insulated flask adapted to receive liquid to a level below the top of the flask; a build-up pipe communicating between the bottom of the flask and the top of the flask above said level; a build-up check valve in the line of said build-up pipe and adjacent to the bottom of the flask, adapted to permit a free flow of liquid from the flask into the build-up pipe but preventing a reverse flow; a pressure closing valve in said build-up pipe between said build-up check valve and the top of the flask adapted to close when the pressure in said build-up pipe rises to a predetermined value and to open when it falls below the predetermined value; a delivery pipe communicating between the interior of said flask below said liquid level and a delivery point exterior of said flask; a liquid evaporator in said delivery pipe between the flask and said delivery point adapted to convert liquid flowing from said flask through said delivery pipe to a gas to be delivered to said delivery point; a delivery check valve in said delivery line between said flask and said evaporator adapted to permit a free flow of liquid through said delivery pipe from said flask to said evaporator but preventing a reverse flow thereof; a pressure relief pipe connected to said delivery pipe at a point between said delivery check valve and said evaporator; a pressure relief valve in said pressure relief pipe adapted to relieve the pressure in said delivery pipe when it rises above a predetermined value; a thrift pipe communicating between said build-up pipe at a point between said pressure closing valve and said flask and said pressure relief pipe at a point between said delivery check valve and said pressure relief valve; a pressure opening valve in said thrift pipe adapted to open when the pressure in said thrift pipe exceeds a predetermined value and to close when said pressure falls below the predetermined value; and a by-pass check valve communicating between said thrift pipe at a point between said pressure opening valve and said pressure relief pipe and said build-up pipe between the junction .of said thrift pipe therewith and the top of the flask.

4. In a converter of the character described, the combination of: an insulated flask having liquid and gas phase sections; a pressure build-up circuit connecting the liquid and gas phase sections of said flask; a build-up check valve in said pressure build-up circuit and immediately adjacent to said liquid phase section, said build-up check valve permitting a flow of fluid from said liquid phase section into said build-up circuit but preventing any sudden reverse flow of fluid; a supply circuit communicating between said liquid phase section and a point of delivery independent of said build-up circuit; an evaporator in said supply circuit and adapted to vaporize liquid supplied thereto by said supply circuit; and a delivery check valve in said supply circuit between said evaporator and said liquid phase section.

5. In a converter of the character described, the combination of: an insulated flask having liquid and gas phase sections; a pressure build-up circuit connecting the liquid and gas phase sections of said flask; a build-up check valve in said pressure build-up circuit and immediately adjacent to said liquid phase section, said buildup check valve permitting a flow of fluid from said liquid phase section into said build-up circuit but preventing any sudden reverse flow of fluid; a supply circuit communicating between said liquid phase section and a point of delivery independent of said build-up circuit; an

evaporator in said supply circuit and adapted to vaporize liquid supplied thereto by said supply circuit; a delivery check valve in said supply circuit between said evaporator and said liquid phase section; and a thrift circuit communicating between said build-up circuit and said supply circuit.

6. A converter according to claim 1 wherein the liquid evaporator is generally conical in shape.

7. A co'nverter according to claim 1, wherein the buildup pipe contains a downwardly sloping section adjacent the bottom of the flask.

8. A converter according to claim 4 wherein the liquid evaporator includes a pair of spaced plates providing a substantially conical passage therebetween with an inlet at the apex of the conical passage and an outlet at the bottom of the passage, the exteriors of said plates being exposed to the ambient temperature.

9. A converter according to claim 5 wherein the thrift circuit includes a bypass check valve adapted to permit a flow of fluid from the supply circuit between said evaporator and said delivery check valve to said build-up circuit.

References Cited in the file of this patent UNITED STATES PATENTS 

